Houston T-Mobile customers with unlocked iPhones get a speed boost

One of the good things about choosing an iPhone that works on AT&T’s network is that you don’t have to use it on AT&T’s network.

Unlock that handset, and you can then take it to T-Mobile, which uses GSM network technology similar to that of AT&T. However, until recently doing this not been a great experience: iPhones on T-Mobile’s network use the older, and much slower, 2G EDGE data service.

But here’s excellent news for Houston GSM iPhone owners: T-Mobile has rejiggered its network here so that unlocked AT&T smartphones can access its faster HSPA+ data service. While it’s not as zippy as LTE, T-Mobile’s HSPA+ offers respectable speeds. On test phones, I’ve seen downloads as fast as 24 Mbps.

As part of this drive, T-Mobile is changing the frequency on which its HSPA+ data network is offered to work with unlocked AT&T devices. The first cities to get this capability were in Kansas City and Las Vegas. On Wednesday, T-Mobile said Houston, Baltimore and Washington, D.C., were added to the list. The Houston coverage area includes the suburbs of Cypress, Jersey Village, Humble, Kingwood and The Woodlands.

Other major cities are partially converted:

T-Mobile network advancements also continue in additional cities including Boston, Chicago, Los Angeles, Miami, Minneapolis, New York metro area, Philadelphia, San Francisco, San Diego and Seattle. Customers in parts of these metro areas are already experiencing improved coverage and iPhone “speed sightings” on T-Mobile’s 4G network.

Note that these faster speeds will only work with the iPhone 4S or iPhone 5, which can talk to HSPA+ networks. It’s not clear if older iPhones can now get T-Mobile’s 3G network speeds in these markets, or if they’ll still be confined to the pokey EDGE service.

The campaign comes as T-Mobile struggles against tough competition from the two largest carriers, AT&T and Verizon, and to a lesser extent, Sprint. Inan earnings report released today, T-Mobile’s sales and profits were both down.

Once T-Mobile has an LTE network up and running, it’s possible Apple would finally offer an iPhone through that carrier. For now, though, T-Mobile customers who want an iPhone will have to make do with a patchwork of HSPA+-enabled markets.